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1 Overview This project is located in an industrial park in Suzhou.
The factory has two floors, and the construction area of each floor is about 36500m2
.
The clean workshop was completed in stages, with a total of 4 stages to complete
.
This project is the second phase.
The 100-class clean workshop is about 2680m2, the thousand-class area is about 580m2, and the common area (testarea) is 5000m2 (the floor plan of the workshop is omitted)
.
2 Main design parameters The main design parameters are shown in Table 1
.
3 Design of clean air-conditioning system 3.
1 Calculation of clean cooling load Summer cooling load includes: maintenance structure cooling load, personnel cooling load, lighting cooling load, production equipment cooling load, fresh air cooling load, air duct cooling loss, air conditioning unit fan load,
etc.
After calculation: 100-level regional cooling load index is 880W/m2, 1000-level cooling load index: 480W/m2
.
Common area (testarea) cooling load index: 600W/m2 (the test equipment is placed in the common area, and the calorific value is large)
.
3.
2 Air-conditioning method of class 100 and class 1000 clean room The clean room adopts the air-conditioning method of FHU+DCU+FFU.
The air-conditioning and airflow organization of the clean room are shown in Figure 1
.
Among them, FHU is the fresh air unit (Freshairhandingu2nit), in addition, the fresh air unit adopts the primary, middle and high efficiency filtration treatment for the fresh air
.
The fresh air unit includes: the initial effect section, the surface cooling section, the middle effect section, the heating section (the manufacturer has a hot water system, and the heat coil is used), the humidification section (the manufacturer has steam), and the high-efficiency section
.
Among them, the manufacturer of the air cleaning section first requires reservation, and then adds a fresh air unit to control the humidity of the clean room, maintain the positive pressure of the clean room and the fresh air demand of personnel
.
The fresh air volume of this project is 35000m3/h; DCU is a dry surface cooling coil (Drycoilunit), and a dry cooling coil is set in the return air clip wall in each clean room
.
The main function of the dry cooling coil is to cool the clean room with constant humidity.
Therefore, the temperature of the chilled water passing through the dry coil is slightly higher than the dew point temperature of the clean room to ensure that the air in the clean room does not condense when passing through the dry cooling coil.
The high-efficiency filter (Fanfilterunit) of the fan, the FFU mixes the return air cooled by the dry cooling coil in the clean room with the fresh air processed by the fresh air unit, and then sends it to the clean room through the high-efficiency filter in the FFU
.
The ground of the clean room adopts a conductive raised floor with a height of 1m, which realizes the form of air supply from the top to the bottom, and further ensures the verticality of the air flow in the form of laminar air supply
.
The characteristics of the air-conditioning method are: the humidity of the clean room adopts the form of centralized control, the control is simple, and the control and management are convenient
.
Secondly, the cooling method of the dry cooling coil is adopted to save the area of the air-conditioning room, which is especially suitable for the clean room places with large area and large cooling load and the area of the air-conditioning room is relatively tight
.
At the same time, the form of multiple groups of dry cooling coils is beneficial for indoor temperature control, especially when the indoor loads are uneven
.
In addition, in the technical interlayer, there will be no condensation water, and it is not easy to hide dirt and breed bacteria
.
However, because the temperature of the chilled water flowing in the dry cooling coil is required to be higher than the dew point temperature of the clean room, the water temperature is too high, which reduces the heat transfer coefficient of the coil, and requires an increase in the heat transfer area of the surface cooling coil, which increases the initial investment cost
.
It is also because the temperature of the chilled water flowing into the dry cooling coil is required to be higher than the dew point temperature of the clean room, while the temperature of the water supply provided by the freezing station is 7°C, and the temperature of the return water is 12°C
.
Therefore, the form of secondary water circulation must be adopted
.
There are two forms of the circulating water system: (1) the form of three-way valve mixing; (2) the form of heat exchanger
.
After analyzing the form characteristics of the two cycles, the form of heat exchanger was finally adopted to further ensure the stability and reliability of the system
.
Of course, to increase the heat exchanger equipment, the investment increases
.
However, compared to this type of project, if a large-area and high-cleanliness clean room is used in the form of an air handling unit, the air duct system of the system will occupy a large space and cost, and at the same time, it will also occupy a large air-conditioning room.
area
.
After comprehensive consideration and comparison, the system using dry surface cooling coil is still economical and reasonable
.
3.
3 Air treatment Air treatment in the clean room: The air in the clean room is first cooled by the dry surface cooling coil to control the temperature in the clean room
.
Keep it within the design temperature range, and then return to the static pressure box at the top of the clean room to mix with fresh air and then send it to the clean room through FFU
.
Air treatment of the fresh air unit: The fresh air enters the cold coil after being filtered by the primary effect.
Loading), enter the secondary heating coil section and humidification section to ensure that the air humidity of the clean room is constant within the design requirements
.
Finally, the treated fresh air is sent to the high-efficiency air supply section by the fan, and then sent to the static pressure box on the ceiling of the clean room, mixed with the return air of the clean room, and sent to the clean room through the FFU
.
The air handling in the 1K locker room is the same
.
4 Air-conditioning main engine and chilled water system This project is the second phase of the project, the main engine has been fully in place in the first phase, a total of 4 sets of 1000RT Carrier centrifugal units are used, all the chilled water pipes have been connected to the required positions, and have been reserved for taking over
.
The testarea and fresh air unit of this project directly use the chilled water of the main chilled water pipe, and the supply and return water temperature is 7°C/12°C; but the chilled water of the dry coil in the clean room must ensure that the chilled water supply and return water temperature is 13°C/17°C ; The design temperature difference between supply and return water is 4 °C, that is, a heat exchanger is used to design a secondary circulating chilled water system
.
An electric two-way valve is installed on the supply and return pipes of the chilled water at the cold source end of the heat exchanger, and controlled by DDC to ensure that the water temperature of the secondary circulation is constant within the design range
.
The secondary chilled water pipe system adopts the method of different procedures.
The dry cooling coils in the return air wall of the clean room are divided into 8 groups.
Each group is equipped with an electric proportional integral valve, and the clean room is sensed according to the corresponding range.
Adjust the opening degree of the proportional integral valve by adjusting the temperature inside, so as to control the temperature within the design requirements
.
The expansion tank is located on the floor
.
5 Automatic control system This phase of the project adopts a set of DDC control system, which is connected with the main station of the computer room, which can realize the local regulation and the control and observation of the operation state of the main station of the computer room
.
The dry cooling coils in the clean room are divided into 8 groups, each group is controlled by a proportional integral valve, the temperature of the area corresponding to each group is detected by multi-point, and the average value of the multi-point PID is used to control the opening of the proportional and integral valve.
, adjust the indoor temperature
.
The humidity is also controlled by multi-point detection.
Through the average PID value of the multi-points, the opening degree of the electric proportional and integral valve of the chilled water of the fresh air unit is controlled by the detected humidity, or the opening degree of the humidification steam valve is controlled to achieve Control the humidity in the clean room within the design range
.
In winter, when the detected outdoor temperature is lower than a certain value, the air will be heated to a certain extent to ensure sufficient humidification to avoid air saturation and insufficient humidification and accumulation of water in the fan section.
affect the filtering effect
.
The fresh air unit adopts frequency conversion control.
According to the actual use area of the clean room, through the opening and closing of the electric air valve, the pressure parameters in the air duct are detected, the fan speed is controlled, and the fresh air volume is adjusted to achieve the purpose of saving energy
.
Both the fresh air unit and the common area air cabinet have a fire protection system that provides a normally closed contact signal.
When a fire occurs in the area, this point will be automatically disconnected, and the fresh air unit and the common area air cabinet fan will stop running
.
6 Engineering debugging Before the clean room test, first clean the clean room, let the air-conditioning system run for 24 hours, and then install the high-efficiency filter and FFU
.
First, ensure that the total fresh air volume is within the design range, and then conduct a positive pressure test between clean rooms.
After repeatedly adjusting the air volume control valve, the basic positive pressure value meets the design requirements
.
However, due to construction and location limitations in the dressing room, the wind speed through the dry coil reaches more than 310m/s, resulting in excessive static pressure in the dressing room.
Because the full pressure of the FFU is about 50Pa, the pressure drop through the dry coil is required to be no greater than 30Pa is appropriate.
On the premise of meeting the cooling load, reduce the wind speed (generally the wind speed is about 2m/s) and reduce the pressure drop of the dry coil
.
After adjustment, the static pressure is restored to the design range and meets the requirements
.
Then adjust the wind speed of FFU one by one to adjust to the design requirements
.
After the air volume and speed design requirements, the high-efficiency filter is tested for leaks, and the unqualified high-efficiency filter is replaced
.
After the above procedures are completed, the cleanliness, self-cleaning time, temperature, humidity, illuminance, floor conductivity, noise, verticality, etc.
are tested, and the test results meet the design requirements and corresponding standards
.
7 Summary (1) Large-area and high-level (higher or equal to 100) clean rooms should be in the form of dry coils, which can save the area of the air-conditioning room and have flexible system control
.
(2) For high-power motor equipment, frequency conversion control technology should be used to reduce energy consumption
.
(3) The air filtration of the fresh air system should adopt primary, medium and high-efficiency three-stage filtration to prolong the service life of the high-efficiency filter
.
(4) Try to use the air organization form that treats the fresh air to the indoor dew point temperature, and reduce the air treatment form that causes unnecessary energy waste due to indoor temperature compensation [3]
.
(5) In the entire clean room system, pay attention to the correct selection and installation of the pressure relief valve
.
The factory has two floors, and the construction area of each floor is about 36500m2
.
The clean workshop was completed in stages, with a total of 4 stages to complete
.
This project is the second phase.
The 100-class clean workshop is about 2680m2, the thousand-class area is about 580m2, and the common area (testarea) is 5000m2 (the floor plan of the workshop is omitted)
.
2 Main design parameters The main design parameters are shown in Table 1
.
3 Design of clean air-conditioning system 3.
1 Calculation of clean cooling load Summer cooling load includes: maintenance structure cooling load, personnel cooling load, lighting cooling load, production equipment cooling load, fresh air cooling load, air duct cooling loss, air conditioning unit fan load,
etc.
After calculation: 100-level regional cooling load index is 880W/m2, 1000-level cooling load index: 480W/m2
.
Common area (testarea) cooling load index: 600W/m2 (the test equipment is placed in the common area, and the calorific value is large)
.
3.
2 Air-conditioning method of class 100 and class 1000 clean room The clean room adopts the air-conditioning method of FHU+DCU+FFU.
The air-conditioning and airflow organization of the clean room are shown in Figure 1
.
Among them, FHU is the fresh air unit (Freshairhandingu2nit), in addition, the fresh air unit adopts the primary, middle and high efficiency filtration treatment for the fresh air
.
The fresh air unit includes: the initial effect section, the surface cooling section, the middle effect section, the heating section (the manufacturer has a hot water system, and the heat coil is used), the humidification section (the manufacturer has steam), and the high-efficiency section
.
Among them, the manufacturer of the air cleaning section first requires reservation, and then adds a fresh air unit to control the humidity of the clean room, maintain the positive pressure of the clean room and the fresh air demand of personnel
.
The fresh air volume of this project is 35000m3/h; DCU is a dry surface cooling coil (Drycoilunit), and a dry cooling coil is set in the return air clip wall in each clean room
.
The main function of the dry cooling coil is to cool the clean room with constant humidity.
Therefore, the temperature of the chilled water passing through the dry coil is slightly higher than the dew point temperature of the clean room to ensure that the air in the clean room does not condense when passing through the dry cooling coil.
The high-efficiency filter (Fanfilterunit) of the fan, the FFU mixes the return air cooled by the dry cooling coil in the clean room with the fresh air processed by the fresh air unit, and then sends it to the clean room through the high-efficiency filter in the FFU
.
The ground of the clean room adopts a conductive raised floor with a height of 1m, which realizes the form of air supply from the top to the bottom, and further ensures the verticality of the air flow in the form of laminar air supply
.
The characteristics of the air-conditioning method are: the humidity of the clean room adopts the form of centralized control, the control is simple, and the control and management are convenient
.
Secondly, the cooling method of the dry cooling coil is adopted to save the area of the air-conditioning room, which is especially suitable for the clean room places with large area and large cooling load and the area of the air-conditioning room is relatively tight
.
At the same time, the form of multiple groups of dry cooling coils is beneficial for indoor temperature control, especially when the indoor loads are uneven
.
In addition, in the technical interlayer, there will be no condensation water, and it is not easy to hide dirt and breed bacteria
.
However, because the temperature of the chilled water flowing in the dry cooling coil is required to be higher than the dew point temperature of the clean room, the water temperature is too high, which reduces the heat transfer coefficient of the coil, and requires an increase in the heat transfer area of the surface cooling coil, which increases the initial investment cost
.
It is also because the temperature of the chilled water flowing into the dry cooling coil is required to be higher than the dew point temperature of the clean room, while the temperature of the water supply provided by the freezing station is 7°C, and the temperature of the return water is 12°C
.
Therefore, the form of secondary water circulation must be adopted
.
There are two forms of the circulating water system: (1) the form of three-way valve mixing; (2) the form of heat exchanger
.
After analyzing the form characteristics of the two cycles, the form of heat exchanger was finally adopted to further ensure the stability and reliability of the system
.
Of course, to increase the heat exchanger equipment, the investment increases
.
However, compared to this type of project, if a large-area and high-cleanliness clean room is used in the form of an air handling unit, the air duct system of the system will occupy a large space and cost, and at the same time, it will also occupy a large air-conditioning room.
area
.
After comprehensive consideration and comparison, the system using dry surface cooling coil is still economical and reasonable
.
3.
3 Air treatment Air treatment in the clean room: The air in the clean room is first cooled by the dry surface cooling coil to control the temperature in the clean room
.
Keep it within the design temperature range, and then return to the static pressure box at the top of the clean room to mix with fresh air and then send it to the clean room through FFU
.
Air treatment of the fresh air unit: The fresh air enters the cold coil after being filtered by the primary effect.
Loading), enter the secondary heating coil section and humidification section to ensure that the air humidity of the clean room is constant within the design requirements
.
Finally, the treated fresh air is sent to the high-efficiency air supply section by the fan, and then sent to the static pressure box on the ceiling of the clean room, mixed with the return air of the clean room, and sent to the clean room through the FFU
.
The air handling in the 1K locker room is the same
.
4 Air-conditioning main engine and chilled water system This project is the second phase of the project, the main engine has been fully in place in the first phase, a total of 4 sets of 1000RT Carrier centrifugal units are used, all the chilled water pipes have been connected to the required positions, and have been reserved for taking over
.
The testarea and fresh air unit of this project directly use the chilled water of the main chilled water pipe, and the supply and return water temperature is 7°C/12°C; but the chilled water of the dry coil in the clean room must ensure that the chilled water supply and return water temperature is 13°C/17°C ; The design temperature difference between supply and return water is 4 °C, that is, a heat exchanger is used to design a secondary circulating chilled water system
.
An electric two-way valve is installed on the supply and return pipes of the chilled water at the cold source end of the heat exchanger, and controlled by DDC to ensure that the water temperature of the secondary circulation is constant within the design range
.
The secondary chilled water pipe system adopts the method of different procedures.
The dry cooling coils in the return air wall of the clean room are divided into 8 groups.
Each group is equipped with an electric proportional integral valve, and the clean room is sensed according to the corresponding range.
Adjust the opening degree of the proportional integral valve by adjusting the temperature inside, so as to control the temperature within the design requirements
.
The expansion tank is located on the floor
.
5 Automatic control system This phase of the project adopts a set of DDC control system, which is connected with the main station of the computer room, which can realize the local regulation and the control and observation of the operation state of the main station of the computer room
.
The dry cooling coils in the clean room are divided into 8 groups, each group is controlled by a proportional integral valve, the temperature of the area corresponding to each group is detected by multi-point, and the average value of the multi-point PID is used to control the opening of the proportional and integral valve.
, adjust the indoor temperature
.
The humidity is also controlled by multi-point detection.
Through the average PID value of the multi-points, the opening degree of the electric proportional and integral valve of the chilled water of the fresh air unit is controlled by the detected humidity, or the opening degree of the humidification steam valve is controlled to achieve Control the humidity in the clean room within the design range
.
In winter, when the detected outdoor temperature is lower than a certain value, the air will be heated to a certain extent to ensure sufficient humidification to avoid air saturation and insufficient humidification and accumulation of water in the fan section.
affect the filtering effect
.
The fresh air unit adopts frequency conversion control.
According to the actual use area of the clean room, through the opening and closing of the electric air valve, the pressure parameters in the air duct are detected, the fan speed is controlled, and the fresh air volume is adjusted to achieve the purpose of saving energy
.
Both the fresh air unit and the common area air cabinet have a fire protection system that provides a normally closed contact signal.
When a fire occurs in the area, this point will be automatically disconnected, and the fresh air unit and the common area air cabinet fan will stop running
.
6 Engineering debugging Before the clean room test, first clean the clean room, let the air-conditioning system run for 24 hours, and then install the high-efficiency filter and FFU
.
First, ensure that the total fresh air volume is within the design range, and then conduct a positive pressure test between clean rooms.
After repeatedly adjusting the air volume control valve, the basic positive pressure value meets the design requirements
.
However, due to construction and location limitations in the dressing room, the wind speed through the dry coil reaches more than 310m/s, resulting in excessive static pressure in the dressing room.
Because the full pressure of the FFU is about 50Pa, the pressure drop through the dry coil is required to be no greater than 30Pa is appropriate.
On the premise of meeting the cooling load, reduce the wind speed (generally the wind speed is about 2m/s) and reduce the pressure drop of the dry coil
.
After adjustment, the static pressure is restored to the design range and meets the requirements
.
Then adjust the wind speed of FFU one by one to adjust to the design requirements
.
After the air volume and speed design requirements, the high-efficiency filter is tested for leaks, and the unqualified high-efficiency filter is replaced
.
After the above procedures are completed, the cleanliness, self-cleaning time, temperature, humidity, illuminance, floor conductivity, noise, verticality, etc.
are tested, and the test results meet the design requirements and corresponding standards
.
7 Summary (1) Large-area and high-level (higher or equal to 100) clean rooms should be in the form of dry coils, which can save the area of the air-conditioning room and have flexible system control
.
(2) For high-power motor equipment, frequency conversion control technology should be used to reduce energy consumption
.
(3) The air filtration of the fresh air system should adopt primary, medium and high-efficiency three-stage filtration to prolong the service life of the high-efficiency filter
.
(4) Try to use the air organization form that treats the fresh air to the indoor dew point temperature, and reduce the air treatment form that causes unnecessary energy waste due to indoor temperature compensation [3]
.
(5) In the entire clean room system, pay attention to the correct selection and installation of the pressure relief valve
.
